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• Trying to concat videos from different sources with ffmpeg and get different broken results every time (partly no audio and/or fast forward video)

  30 octobre 2022, par Oliver

  I am using ffmpeg for years to create (merge and render) big video files from the (vaction) clips my sony camcorder produces. My basic workflow is to copy the mp4 files from the camcorder over to my pc, put the names in a file (file 'filename') and use the following command to create one big file that is playable by my apple tv :

  


  ffmpeg -f concat -safe 0 -i filelist.txt -c:v libx265 -preset slow -x265-params strong-intra-smoothing=0:merange=58 -crf 24 -c:a aac -b:a 320k -tag:v hvc1 output.mp4


  


  i cannot explain most of the arguments in total detail but i know that it works.
My problem occurred as i wanted to prepend some video clips recorded with an iphone to one of those files. So the first part seemed easy, the sony camcorder files have a resolution of 3840x2160 and the iphone video clips have a resolution of 1280x720 so at first i upscaled the iphone files using this command (i would have rather done in just one step but i do not know how to do that) :

  


  ffmpeg -i IMG_1182.MP4 -vf scale=3840:2160 IMG_1182_3840x2160.MP4


  


  then i just tried to add those upscaled video files to the filelist from the first command and ran the command for all clips again. Sadly that did not worked, as the resulting file contained all clips but only the iphone part had audio ! For the rest of the video the audio was missing. At this point i also did not noticed that the second part was played much faster (like played in fast forward mode). So guessed that i have to render the iphone and sony camcorder clips separately using the first command. That worked and i got two video files with perfect audio and video. My next step was to concatenate the resulting files using the following simple command :

  


  ffmpeg -f concat -safe 0 -i concatlist.txt -c copy output.mp4


  


  where concatlist contained both files.
Sadly that also did not worked. I do got a file containing both parts, this time with audio, but the video of the second part still was fast forward !

  


  I do not know what to do at this point, and i also do not understand enough to experiment with the options any more. Can someone explain to my what could be the problems here and how to solve them ?

  


• Add audio to video file at specific second in nodejs fluent-ffmpeg

  17 mars 2020, par toljoas

  I have a Video (mp4) and want to add audio to it (mp3).
  The audio should be added at the xth second of the video (meaning the video initially plays for 3 seconds, and only then the audio starts to play, if possible only for a specified duration, but this is not necessary).
  I use the package ’fluent-ffmpeg’.

  I have tried the following :

  const conv = ffmpeg()
  
  
  
  conv.addInput(__dirname + '/screens/screen_%d.png').
  
  addInput(__dirname + '/audio.mp3').setStartTime(3).setDuration(6).
  
  withFpsInput(60).withSize('1920x1080')

  But this sets the start time of the audio itself (meaning the first 6 seconds of the audio are skipped), and sets the duration of the whole video, not merely the audio.

  The question I am asking has already been asked here, but the answer merely shows how to add audio to the video from the start of the video.

  Help is appreciated.

• Cannot open ".mp4" video files using OpenCV 2.4.3, Python 2.7 in Windows 7 machine

  24 octobre 2017, par TJ Monserrat

  I am currently working on a project that involves reading mp4 video files.
  The problem I encountered is that it using Python 2.7 (32 bit), OpenCV 2.4.3 (cv2.pyd) in a Windows 7 machine.

  The code snippet is as follows :

  try:
  
          video = cv2.VideoCapture("video.mp4")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" always returns false : meaning it doesn’t read the file "video.mp4"
  But when we try this :

  try:
  
          video = cv2.VideoCapture("video.avi")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" returns true : meaning it is able to read ".avi" files.

  Another is we have tried this same snippet on Linux and Mac and it seems to work fine, meaning it is able to read both mp4 files and avi files.

  This problem is similar to this problem and this problem. Both still don’t have a clear and workable answer.

  I would appreciate any help or workaround aside from just using Linux or Mac for programming this as I need this to work on all three systems.